Electromagnetic pump system



July 27, 1965 R. s. BAKER 3,196,795

ELECTROMAGNETIC PUMP SYSTEM Filed Jan. :2, 1963 5 sheets-sheet 2 |22|2o\ oo flae -IOZ- E- j /Z f i l |04/ |03 |05\} u2 'I3 Y INVENTOR`RICHARD sl BAKER nOg/M492 `AGENT July 27, 1965 R. s. BAKER 3,196,795

ned Jan. 2, 196s 5 sheets-sheet :s

July 27, 1965 R. s. BAKER ELECTROMAGNETIC PUMP SYSTEM 5 Sheets-Sheet 4Filed Jan. 2, 1963 INVENTOR.

RICHARD' S. BAKER AGENT July 27, 1965 R. s. BAKER ELECTROMAGNETIC PUMPSYSTEM 5 Sheets-Sheet Filed Jan. 2, 1963 INVENTOR.

RICHARD S. BAKER AGENT United States Patent O 3,195,795 ELECTROMAGNETICPUMP SYSTEM Richard S. Baker, Northridge, Calif., assigner to NorthAmerican Aviation, Inc.

Filed Jan. 2, 1963, Ser. No. 248,935 7 Claims. (Cl. 103-1) The presentinvention relates to an electromagnetic pump system for the transfer ofelectrically conductive liquids and more particularly to anelectromagnetic interaction pump system for the transfer of hightemperature liquid metals. The improved pump system of the presentinvention is based upon the principle of operation of my helical rotorelectromagnetic pump disclosed in United States Patent No. 2,940,393,issued June 14, 1960, and assigned to the same assignee as the presentinvention.

Although conventional mechanical and electromagnetic pumps are generallywell-known in the prior art, modern foundry practice depends primarilyon gravity and Siphoninduced flow arrangements to transfer liquidmetals, particularly very high temperature liquid metals such asaluminum, zinc, nickel, brass and the like. Conventional mechanicalpumps for practical reasons have been limited in modern foundry practiceto `low temperature, noncorrosive liquid metals. These pumps cannot beused for pumping high temperature liquid metals since the moving partsgenerally formed from iron or steel rapidly deteriorate in the corrosiveenvironment of most liquid metals.

Electromagnetic pumps are adapted for use in modern foundry practice,particularly in the transfer of conductive liquids, since there are nomoving parts in contact with the liquid being pumped. The magneticimpeller in an electromagnetic pump replaces the mechanical impeller ofa mechanical pump. Electromagnetic pumps develop a pumping force byconverting magnetic energy into pressure energy in accordance with theelectromagnetic thrust that is generated by the passage of an electriccurrent, either applied or induced, through an electrically conductiveliquid transversely to a magnetic field. The direction of force actingupon the conductive liquid and the resulting liquid motion aredetermined by the well-known three nger rule of electrophysies.

The maior problem in the operation of any electromagnetic pump in modernfoundry practice is the vulnerability of the conductors and theinsulation in the field winding to high temperature. rl`his factor iscommonly the result of high temperatures associated with the liqiudmetal being pumped. For example, electromagnetic conduction pumps haverelatively heavy conductors or bus bars which serve as electrodeconnections to the pumping section. These bus bars are generally securedto the pumping section by bre-.zing or welding and are thereforesusceptible to breaking away from the pumping section when a hightemperature liquid metal is being pumped. When the bus bars in aconduction pump are formed from materials having better metallurgicalproperties, lower pump efficiencies result which are frequently nogreater than 2 or 3 percent in pumps having any appreciable capacity.Linear induction pumps which operate on the theory of an induction motorgenerally require eX- pensive polyphase field windings. An electricalcurrent is induced in the liquid metal being pumped by a magnetic fieldset up by alternating currents flowing in windings in a magnet structuresurrounding the pump section. While efiicient pumping generally results,induction pumps are expensive, structurally expansive, and susceptibleto the high temperature factor.

Modern foundry practice, therefore, has had to depend primarily ongravity and Siphon-induced ow arrangements to transfer liquid metals,particularly the very high temperature liquid metals. The transfer ofthe liquid CII 3,196,795 Patented July 27, 1965 ICC metal or melt infoundry practice is preferably without excessive agitation of the meltand without rupture of a protective oxide skin that forms on the surfaceof the melt. This oxide skin substantially reduces both the gasadsorption by the melt and the related accumulation of dross or slagtherein. When the oxide skin remains unbroken and the melt transfer iscalm, a relatively clean molten metal results that is suitable forpouring high quality castings having a desirable low porosity. Withoutexacting control provisions, the gravity and Siphoninduced transfer Howscurrently used `by modern foundry practice substantially increase theprobability of high gas adsorption by the melt since rupture of theoxide skin and excessive agitation of the melt are unavoidable.

A rotating field electromagnetic pump is particularly adapted for thedesired calm transfer of liquid metals in modern foundry practice.However, high temperature liquid metals require an improved field coilwindingr and rotor geometry which promotes adequate cooling andsubstantially increases the efliciency of the pump during hightemperature pumping. The necessary bearing arrangements in rotatingfield electromagnetic pumps are also subjected to the hightemperatureenvironment. It is desirable to position the bearing arrangements for arotating eld pump in a region removed from the high temperatureenvironment without sacrificing stability of the rotating pumpcomponents.

Accordingly, it is a primary object of the present invention to providean electromagnetic pump system for pumping electrically conductiveliquids, particularly high temperature liquid metals.

It is also an object of the invention to provide an electromagnetic pumpsystem that pumps a liquid metal from beneath the surface of a meltwithout rupture of the protective oxide slrin on the melt surface.

A further object of the invention is to provide an electromagnetic pumpsystem which transfers the liquid metal from one location to anotherwithout an appreciable increase in `gas adsorption by the melt orrelated dross formation therein.

Another object of the invention is to provide an electromagnetieinteraction pump system for pumping electrically conductive liquidsagainst the action of gravity -by developed electromagnetic forces.

Yet another object of the invention is to provide an electromagneticpump system that develops a pumping action by the production of a forceon the liquid in the desired direction of flow by an electromagneticinteraction that is produced by the helical geometry of the pump rotor.

It is also an object of the invention to provide an electromagnetic pumpsystem with adequate cooling of the helical pump rotor.

Yet another object of the invention is to provide an electromagneticpump system having an improved bearing arrangement for the helical pumprotor.

An additional object of the invention is to provide an electromagneticpump system that develops a calm ow of liquid metal under pump inducedpressure without complex guide vane configurations in the pump liquid owpassages.

Likewise an object of the invention is to provide an electromagneticpump system that facilitates accurate control of the l'low of a liquidunder pump induced pressure.

A further object of the invention is to provide a method and apparatusto stir a melt to maintain homogeneity thereof.

Yet another object of the invention is to provide a method and apparatusfor substantially cleaning pump system ow passages of liquid by areversal of the developed electromagnetic forces.

Further objects, features and the attending advantages of the inventionwill be apparent with regard to the following description read inconnection with the accompanying drawings in which:

FIGURE 1 is a perspective view, partly broken away, of one form of theelectromagnetic pump system of the invention;

FIGURE 2 is a perspective view of the pump system of FIGURE 1 in anoperating location;

FIGURE 3 is a longitudinal section, partly schematic, of the pump systemof FIGURE l;

FIGURE 4 is a perspective view of another form of the electromagneticpump system in an operating location;

FIGURE 5 is a perspective view, partly broken away, of the pump systemof FIGURE 4;

FIGURE 6 is a longitudinal section, partly schematic, of yet anotherform of the electromagnetic pump system of the invention; and

FIGURE 7 is both a perspective view and a developed view of one form ofmy helical pump rotor as disclosed.

Briefly, in accordance with one form of the invention, anelectromagnetic pump system for pumping electrically conductive liquidsis provided having at least one pump region that is juxtaposed between amagnetic helical rotor, which sets up a magnetic flux field across thepump region and distributes the field in a generally helical curve, anda flux return path so that when the rotor is rotated by a suitable drivemeans, the magnetic flux tield induces electrical eddy-currents in aliquid in the pump region that flow in patterns which conform with thehelical geometry of the rotor and interact with the magnetic tield toimpart desired pumping forces on the liquid in the pump region.

Referring to FIGURE 1, one form of the electromagnetic pump system ofthe invention has an outer crucible member 10 supported by a pluralityof refractory bricks 12 or the like. The bricks 12 protect the pumpsystem components and provide thermal insulation for the pump system. Aradially extending ange 13 of the crucible 19 provides a bearing surfaceor platform for a lip edge 15 of an inner crucible member 16 that isnested within the outer crucible. Both the outer and inner crucibles 10and 16 are oriented in a generally vertical alignment about a verticalaxis. It is contemplated that the certain degrees of tilt from thevertical alignment shown by FIGURES 1 and 2 also are within theinventive concept. A spring clamping means, not shown, can be providedto ensure the relative positions of the crucibles 10 and 16 since theinner crucible 16 may have a tendency to be buoyed up when certainliquid metals and their alloys are being pumped by the pump system ofthe invention.

The outer and inner crucible members 1t) and 16 are preferably formedfrom a suitable refractory material such as silicon carbide, boronnitride and the like. The particular metal or refractory materialutilized for the flow passages of the pump system is not critical to theprinciple of operation of my electromagnetic pump system. The choice ofmaterial is a function of pressure, type of liquid being pumped, andtemperature; the flow passages should be particularly adapted towithstand high operating temperatures such as those incurred whenpumping molten metals like aluminum, zinc, brass and the like. While thecrucible members 10 and 16 are shown by FIGURE 1 as integral, individualunits that are preformed from a refractory material, it is contemplatedthat for ease of construction and assembly the members 10 and 16 couldbe sectionalized, bonded together by a suitable mortar or sealing agent,and built up into the generally cup-shaped crucible members.

In the nested arrangement, the outer and inner crucible members 10 and16 are spaced apart to develop a pump region or annulus 20 therebetween.The crucible members also form an inlet region 21 that communicates withthe pump annulus 20. The lip edge 1.5 of the inner crucible 16 developsan outlet region or discharge scroll 22 that also communicates with thepump annulus 2t). Suitable spacer members, not shown, may be providedbetween the nested outer and inner crucibles 10 and 16.

At least one inlet port 25 and one outlet port 26 communicate with theinlet region 21 and the outlet region 22, respectively, as shown byFIGURE l. The inlet port 25, while shown in the side wall of the outercrucible 10 can also be positioned in the bottom wall of the outercrucible. Further, the inlet port 25 can be tangentially directed withregard to the inlet region 21. It is contemplated that more than oneingress duct can communicate with the inlet port 25 of the pump systemso that melt can be pumped from one or more levels beneath theprotective oxide skin on the surface of a melt body. The gentle pumpingaction developed by the electromagnetic interaction pump system of theinvention further ensures a clean liquid metal for subsequent pouringwithout rupturing the oxide skin during pumping.

If any dross or slag accumulation should occur in the pump annulus 20 orits related regions 21 and 22, the nested arrangement of the outer andinner crucibles 10 and 16 facilitates the removal of the inner crucibleto expose such accumulation for easy cleaning by mechanical tools andthe like. However, during pumping, the continuous scrubbing of the pumpannulus 2t) by the developed pumping action, to be subsequentlydescribed, minimizes such dross or slag accumulation therein andmaintains a relatively clean pump annulus at all times. Thus the needfor mechanical tools to clean the pump annulus 20 and the inlet andoutlet regions 21 and 22 is substantially avoided by the structuralarrangement and principle of operation of the present invention.Although it is not critical to the operation of the present pump system,the bottom wall of the outer crucible 10 may slope to facilitatedrainage of the inlet region 21, the pump annulus 20, and the outletregion 22.

FIGURE 2 shows one form of a structural beam arrangement 30 for theelectromagnetic pump system when the pump system is positioned adjacentto a melting furnace or hold pot 32 such as those well-known in thefoundry art. The pump system of the invention can also be positioned,for example, between one or more melting furnaces and hold pots, or anycombination thereof, or between separate hearths of one or morereverberatory furnaces, or at any other location in a foundry operationwhere it is desirable to transfer liquid metal.

A prime mover, such as an electric drive motor 35, is supported andpositioned by the bearn arrangement 30 above the nested crucible members10 and 16. A rotor shaft 36 is connected to the drive motors 35. Theshaft 36 can be either solid or hollow, the latter being particularlydesirable for the introduction of a cooling medium such as air to therotating pump components subsequently described. A suitable bearingarrangement 38, more clearly shown by FIGURE 1, rotatably positions therotor shaft 36 so that the shaft depends into the cup region of theinner crucible 16. The bearing arrangement 3S is positioned above andexternal to the volume defined by the pump annulus 29 and the inletregion 21. This arrangement removes the bearings from the primary hightemperature environment developed during the pumping of high temperatureliquid metals and permits adequate cooling by the open location.

A helical rotor 40 is field wound and can be attached to or integrallyformed with the rotor shaft 36. The helical rotor 40, as shown in FIGURE1, has the form of a two-pole electromagnet with pole pieces 42 and 43;however, the helical rotor 40 can also have a cruciform or any othersuitable multipolar form. Both the rotor shaft 36 and the helical rotor40 are preferably formed from a magnetic material such as mild carbonsteel. The helical rotor 40 is formed with at least one helical thread45.' more clearly shown by FIGURE 3. It is desirable that both the pitchor the helical thread 45 and the width of the thread crest permit aseparation between adjacent thread traces on one side oi the rotor 49 toreduce flux leakage paths. Further, it is desirable that the helicalthread l5 have a sulicient trace length to travel approximately theaxial lcngtlLoi the pump annulus 20 during rotation of the helical rotorlli?.

A field coil winding 47 is wound in the thread t5 between the adlacentpoles 42 and 43 of the helical rotor di). The field coil winding 7 ispreferably formed from silicone-impregnated double glass insulatedcopper wire which particularly adapted for high temperature operatingconditions. For rotor operating temperatures in the range 600 F. to 1lG0F., nickel-clad copper wire with ceramic insulation is preferred. Thefield winding 47 is insulated from the rotor lo by means of glasssaddles or blades, not shown. Thos also serve to produce ventilatingducts or i'iow passages between the rotor and the winding. The fieldcoil winding 47 is electrically connected to an external direct currentpower source, not shown, by means of suitable slip rings 49. The fieldwind- -fl' is connected so that adjacent eld poles, such as pole pieces42 amv 43, produce magnetic poles of opposite polarity. All the turns ofthe field coil winding 47 on each pole piece 42 and i3 act along thesame axis, thereby concentrating the magnetomotive force. This makes thei elical rotor electromagnetic pump particularly suitable for use wherethe pump annulus 20 must be relatively thick-walled. The slip rings 49are connected through `iifzihle brushes and leads to the external powersource. A plurality of clamping strips or bands 50-52- retain the fieldcoil winding 47 within the helical thread 45.

A protective iaclrct S5 can be secured to and generally enclose thehelical rotor 4i). The jacket 55 is preferably to mcd from a suitablematerial such as stainless steel and prot-3c s the field coil winding 47from the effects of high temperature operating conditions when handlingmolten metals. Based upon design parameters, additional l transferbarriers, in addition to the jacket 55, can be L ioned within the innerCrucible i6 between the periphery of the helical rotor f-ll and the wallof the Crucible whis maint a cool?. t flow path therebetween.

The rotating pump components` which include the rotor .tinto thegenerally cup-shaped interior ofthe inner lc member 16 with t .e pumpannulus 20 generally ,iacent to the helical rotor fit). The pump annulustot in tluiil communication with the rotating comporlli-e mechanicallyrotating co nponents therefore are not weit-:d by direct immersion inthe liquid metal nt is being pumped. The geometry of the helical rotor oand the field coil winding i7 complements the cupsiaped inner Cruciblemember lo and provides an unobstructed 'low of co" ing air to therotating pump compole niain lining a total nominal air gap which insuresa hiyc i, eru rotor ele; netic pump system. if a higher flow rate isdesired, suitable blower arrangements auch as those llnown in the artcan oe utilized to inet ^sc the normal .ir'ow.

ly constructed in. gnetic structure 5S is arranged mir-cent to the pumpregion cr annulus 2t) and provides a tlux return path to improve theover all pump system efficiency by reducing-g lo ige flux. The magneticstructure 58 is preferably bi t-up from a plurality of laminationsformed from a goed c .de of magnetic material as silicon steel which maybe individually coated with a suitable insulating material. It isgenerally desirable, particularly when pum ng high temperature liquidmetals, to maintain the magnetic structure 53 at a temperature that sthan the Curie temperature of the laminations. A cooling medium, such asair, is introduced to the i iagnetic structure 5S from an externalsource, not shown, through at least one inlet conduit Si). A plenumregion or tube distributes the coolng air to a plurality of similarcircumfercntially spaced ducts 62, and then ex- 5 liausts the coolingair from the magnetic structure through at least one dischargepipe 63.

In operation, the field coil winding 47 of the electromagnetic pumpsystem shown by FIGURE 1 and 2 is energized from the direct currentpower supply, not shown, so that the helical rotor 45t as a source ofmagnetic flux has alternate north and south polarities skewedcircumferentiiilly and axially relative to the axis of rotation of thehelical rotor. The helical rotor 40 is not homopolar in my helical rotorpump since the opposing north and south polarities develop relatedopposite polarities in the regions immediately adiacent to the rotorshaft 36. The magnetic flux field set up by the energization of thefield winding 4'/ is more clearly shown by FIGURE 3. The magnetic fluxeld passes from the skewed north poles of the helical rotor 48 throughthe pump annulus 26 and the conducting liquid therein to the flux returnpath provided by the niagnetic structure S8. The magnetic field dividesinto at least two llow paths, each of which returns to the regionsimmediately adjacent to the skewed south poles of the helical rotor 49.The flux field then passes back through the pump annulus 2t) to thesouth poles. The direction of the magnetic flux lield in the pumpsection 20 is substantially radial to the axis of rotation of thehelical rotor 49, and is distributed in tlux patterns or paths thatdefine at least one generally helical curve about the rotor.

Rotation of the energized field wound helical rotor 4i), for example, ina counter-clockwise direction, i.e. from left to right as viewed inFGURES 1 and 2, develops a variance in the magnetic ux field across thepump region or annulus 2l). Referring to FIGURE 7, this variance inducesvoltages such as along current paths A-B and C-D in the pump annulus 20in accordance with the right-hand rule of electrophysics. These voltagesinteract with the magnetic tiel-:l to produce the electromagnetic thrustor force F on the conducting liquid in the pump annulus 2li inaccordance with the left-hand rule of electrophysics. My helical rotorpump develops the resultant vector force F that has both axial andcircumferential vector components, fa and fc respectively. Thedevelopment of the axial component fa permits the use of a partionlcsspump region such as pump region 2i) shown by FIGURE 1, since the axialcomponent fa imparts a desired velocity V to the conducting liquid andresults in axial liquid flow through the pump region under pumpiriduc-cu pr ssures. The forces, such as force F, that are impressedupon the liquid metal in the pump annulus 20 ot` FIGURE l move or pumpthe liquid metal from the inlet port 25 to the outlet port 26. Themovement of the liquid meta in the pump annulus 2i) will continually "ubor liush the annulus of any dross or slag accumul: on therein. Whip orrunout chaructcriC s of the Clepcnding pump components also areminimized oy thc energizatioii of the i ald winding 4'! which assists inObtaining virtually vibrationlcss running characteristics of therotating pump Components. Por example, in one test run, .004 inch runoutor variance from the vertical axis of rotation was observed for therotating pump componcnts without field cnergization. When thc fieldwinding 7 was encrgizxl, the magnetic field set up by the helical rotorgeometry significantly reduced the rcnout to .OS2 inch.

The directionalizcd laminar flow of the molten metal under the pumpinduced pressures created by the described electromagnetic forcesprovides a rclati '-ly calm liquid tlow from the outlet port 26 with aminimum of turbulence. While the outlet port 21S is tangentiallydirected to the outlet region 22 and contributes to the calm flow, thetangential attitude is not critical to the operation of the pump systemofthe invention.

The introduction of the pumped metal from the discharge or outlet port25 to a closed conduit 27 for transfer to another location also reducesthe probability of additional gas adsorption and related drossaccumulation by the melt. If necessary, the Conduit 27 may bc suitablyinsulated or heated to minimize temperature losses in the liquid metalduring transfer. Thus, the pumped metal fiows under pump inducedpressure at a near optimum pouring temperature without requiringadditional heating in a subsequent holding or pouring ladle, not shown.The liquid metal also can beA pumped at the near optimum pouringtemperature without requiring prior overheating in the melt body tocompensate for subsequent temperature losses during transfer such asthose experienced in the known prior art pump systems.

Accurate successive or continuous flow of liquid metal under pumpinduced pressures is achieved by control of either the drive motor 35,the energization of the eld winding 47, or both, so that measured flowand instantaneous stoppage of the calm liquid flow from the pump systemof the invention is possible. For example, in one pump system formed inaccordance with the invention, a 25 ampere field current was maintainedin the eld winding 47 when the drive motor 35 was stopped. A prior 3000gallons per minute discharge ow from the pump system rapidly decreasedto zero flow with a time constant of three seconds. The field currentwas turned off only after the discharge flow of liquid metal hadterminated.

Known gravity or syphon transfer arrangements require approximately onehour to transfer 40,00() pounds of a liquid metal, such as aluminum,with no assurance of a calm metal ow. One of my electromagnetic pumpsystems pumps 500 gallons per minute and transfers 600,- 000 pounds ofaluminum in one hour; the transfer being accomplished with a calmlaminar ow and under pump induced pressure against' the effects ofgravity by use of the previously described electromagnetic forces.

The electromagnetic pump system particularly shown by FIGURES 1 and 2will pump 262() gallons per minute at a developed pressure of 31.5p.s.i. when the helical rotor 40 is driven at 374 r.p.m. with a directcurrent input to the field winding 47 of 28 amperes total at 200 volts.When the rotor is driven at constant speed, the discharge flow from thepump may be varied by a field rheostat in series with the direct currentpower source for the field winding 47 to obtain a smooth, steplessvariation of iow and pressure.

A simple reversal of the drive motor 35 provides reverse travel ofliquid in the pump region or annulus 20 to rapidly clean the dischargeport 26, conduit 27, and related flow passages of liquid metal. Thisavoids solidication of liquid metal in the tlow passages during periodswhen no liquid flow is desired.

FIGURES 4 and 5 show another form of the electromagnetic interactionpump system of the present invention. The principle of operation issimilar to the pump system shown by FIGURES l and 2. The pump systemshown by FIGURES 4 and 5 operates in a partly submerged position in aliquid metai pool or body of melt 65. The melt 65 may be contained bysuitable bricks 66 or other suitable structure common to foundrypractice.

FIGURE 4 shows one form of a structural beam arrangement 68 positionedgenerally above the melt 65 and bearing upon the bricks 66. Othersupport arrangements are also contemplated to be within the concept ofthe pump system being described and the arrangement 68 shown by FIGURES4 and 5 is not critical. A support ring 70 is retained by the beamarrangement 68 and engages a radially extending flange portion 72 of anouter channel portion 73. The outer portion 73 is spaced from andcircumjacent to an inner Crucible portion 75 to develop a pump region orannulus 76 therebetween.

The outer and inner portions 73 and 75 respectively are shown by FIGURE5 as an integral unit either preformed from metal or a suitablerefractory material such as those materials previously described. It isagain contemplated that for ease of construction and assembly theportions 73 and 75 can be sectionalizcd and built up into the generalconfiguration as shown by FIGURE 5. If

desired, suitable spacer members, not shown, can be provided between theouter and inner portions.

The structural beam arrangement 63 also supports a prime mover, such asan electric motor 78, with a depending rotor shaft 79 connected thereto.A field wound helical rotor 80, similar in all structural aspects to thefield wound helical rotor 40 shown by FIGURES 1 and 2, is secured to orintegrally formed with the rotor shaft 79. The helical rotor S0 dependsinto the inner Crucible portion 75 so that the pump annulus 76 isgenerally circumjacent to the rotor.

A magnetic structure 84provides a return path for the magnetic ux fieldset up by the magnetic rotor. The magnetic structure 84 is positionedwithin the outer channel portion 73 and is preferably formed from aplurality of mild steel laminations. The magnetic structure 84 may alsobe supported from the beam arrangement 68 to reduce the loading on theouter channel portion 73, particularly when the channel portion isformed from a refractory material. Secondary insulating barriers 86 and87, formed from asbestos or the like, are positioned between themagnetic structure 84 and the walls of the outer portion 73 to reducethe heat transfer from the melt .65 t0 the magnetic structure 84. Acooling medium, such as air, is introduced to the magnetic structure 84through an inlet conduit 90 to maintain the laminates below their Curietemperature. The cooling air passes from the inlet conduit 90 to aplenum region or tube 91 and then exhausts from the magnetic structure84 through a plurality of cricumferentially spaced ducts, such as duct92. It is contemplated that additional heat transfer barriers, similarto heat barriers 86 and 87, may be positioned within the inner crucibleportion 75 between the periphery of the helical rotor Si! and the wallsof the inner portion 75.

The pump annulus 76 is open to the melt 65 on a plane that is suitablyspaced from the hearth or pot bottom 94. Ingress of molten or liquidmetal to the pump section 76 during operation of the pump system, shownby FIG- URES 4 and 5, develop-s a gentle swirling or stirring action inthe melt 65 which assists in maintaining a hornogenous melt and aids inthe escape of absorbed gases in the melt without rupture of theprotective oxide skin on the melt surface.

Operatively, the electromagnetic pump system shown by FIGURES 4 and 5develops a pumping action similar to that previously described withregard to the pump system shown by FIGURES 1 and 2. The electromagneticforces developed within the pump section 76 upon the electricallyconductive liquid therein are in accordance with those forces previouslydescribed and effect the lifting and conveying of the liquid metal to anoutlet or discharge conduit 97.

FIGURE 6 shows yet another modification of the electromagneticinteraction pump system of the invention. Again the theory and principleof operation is similar to that previously described with regard to thepump systems of my invention as shown by FIG- URES 1-5.

The helical rotor is positioned generally circumjacent to a pump regionor annulus 102 as shown by FIGURE 6. A magnetic structure 103,structurally similar to those previously described, is positioned withinan insulating core member 104 and provides a flux return path means. Thecore member 104 is centrally positioned within the volume defined by thepump annulus 102 by a plurality of spacer members similar to spacermember 105.

An external drive means, such as an electric motor 110, rotates thehelical rotor 100 through a suitable power transmission means, such asthe intermeshing spur gear arrangements 112 and 113. The powertransmission gear arrangements are not critical to the operation of theinveniton and are shown only as an illustration of suitablearrangements,

A lield winding 120 threaded on the skewed poles of the helical rotor100 is energized from an external direct current power supply, notshown, through well-known leads and brushes cooperating with suitableslip rings 122. When the eld winding 12) is energized and the helicalrotor 13S driven by the drive motor 1li), the electrically conductiveliquid in the pump annulus $.02 moves from an inlet port 125 to anoutlet port 126 by the forces imparted in the pump annuius.

The electromagnetic pump system shown by FIGURE 6 is particularlyadapted for operation in a horizontal orientaiton. However, it iscontemplated that the pump system can be use in a generally verticalorientation such as shown for the pump systems of FIGURES 1 and 5.

The .elical rotor electromagnetic pump systems, as shown and described,offers distinct advantages over known mechanical pump systems and otherelectr magnetic pump systems, i.e. induction and conduction pumps. Thehelical rotor pump system 'nas (l) no moving parts in contact with theliquid being pumped, (2) no seals or stuffing boxes required, and (3)operability in either horizontal or ver "al orientati n.

In addition, the helical rotor pump system of the invention offersseveral unique features: flow rates are easily varied; highly efficientoperation; reduced entrance losses so that the pump system can operateat low net positive suction with cavitation; large running clearancesbetween the rot. ting pump components and the pump region components;concentrated fie'd winding sets up a strong magnetic field across a widegap which makes it possible to use a thick-walled pump channel orregion; operational tieni' since the rotating pump compoen.s are notsecured to the pump r on components; and no capacitors are required forpower factor correction since direct current is preferably used to setup the magnetic field.

As will be evidenced from the certain aspects of the invencn are notlimited to the particular details of construction as illustrated. Whilethe Source of magnetic flux is shown by FlGURES l-6 as a helical rotorwith a field wi 'ug suitably energized, the magnetic flux can bedevclopd by suitably arranged permanent magnets sltcwed to form ahe.ical rotor, or by a combination of elecL magnets and permanentmagnets. A skewed or helical psrtnanent magnet rotor as a source oi'magnetic ilus/ ticulsr use in small pump systems to develop the magneticfo ces on the liquid being pumped. it is contemplated that ohcrmodications and 3 lied in the art. Accordingiy, it is intended that ta:appended claims shall cover such modifications and applications that donot depart from the true spirit and scope of the invention.

Having described my invention, what I claim and desire to secure byLetters Patent of the United States is:

i. An electromagnetic pump system for pumping electrically coductiveliquids comprising:

(a) first and second generally cup-shaped members,

(b) a rim portion on said first cup-shaped member cooperating with a rimportion on said second cupshaped member to nest said first member withinsaid second member in a spaced apart relationship to each other,

(c) a pump region developed between said first and second members,

(d) at least one inlet port to said pump region in said second member,

(e) at least one outlet port form said pump region,

(f)` a field wound helical rotor rotatably positioned within said firstcup-shaped member and spaced therefrom to define a coolant flow path,

(g) support means for said helical rotor including a bearing arrangementremoved from said lirst cupshaped member,

(h) flux return path means circumjacent to said pump region,

foregoing description,

(i) cooling means for said ux return path,

(j) means electrically connecting said field wound rotor to a powersource to set up a substantially radial magnetic flux field across saidpump region distributed in at least one helical curve about said vrotor, and

(k) drive means to rotate said helical rotor so that the magnetic fieldinduces eddy-currents in a conductive liquid in said region which flowin paths that conform with the helical geometry of said rotor means andinteract with the magnetic field to impart pumping forces on the liquid.

2. The pump system of claim 1 in which said pump region is an annulus.

3. The pump system of claim 1 in which said cupshaped members are formedfrom a suitable insulating material.

4. An electromagnetic pump system for pumping electrically conductiveliquids comprising:

(a) an inner Crucible portion,

(b) an outer channel portion generally circumjacent to said innerportion and spaced therefrom,

(c) a pump region developed between said inner and outer portions,

(d) at least one outlet port from said pump region,

(e) a field wound helical rotor rotatably positioned within said innerCrucible portion and spaced therefrom to develop a coolant ow path,

(f) support means for said helical rotor and said inner and outerportions including a bearing arrangement removed from said inner andouter portions,

(g) flux return path means positioned within said outer channel portion,

(h) cooling means for said flux return path,

(i) means electrically connecting said field wound rotor to a powersource to set up a substantially radial magnetic flux fluid across saidpump region distributed in at least one helical curve about said rotor,and

(j) drive means to rotate said helical rotor so that the magnetic fieldinduces eddy-currents in a conductive liquid in said region which flowin paths that conform with the helical geometry of said rotor means andinteract with the magnetic field to im part pumping forces on theliquid.

5. The pump system of claim 4 in which said pump region is an annulus.

6. The pump system of claim 4 in which said cupshaped members are formedfrom a suitable insulating material.

7. An electromagnetic pump system for pumping electrically conductiveliquids comprising:

(a) a central core member, l

(b) flux return path means positioned within core member,

(c) a field wound helical rotor rotatably positioned circumjacent tosaid core,

(d) a pump region juxtaposed between said helical rotor and said fluxreturn means,

(e) at least one inlet and outlet port from said pump region,

(f) means electrically connecting said field wound rotor to a powersource to set up a magnetic flux eld across said pump region, and

(g) drive means to rotate said helical rotor so that the magnetic fieldinduces eddy-currents in a conductive liquid in said region which flowin paths that conform with the helical geometry of said rotor means andinteract with the magnetic field to impart pumping forces on the liquid.

said

(References on following page) References Cited by the Examiner UNITEDSTATES PATENTS Newcomb 103-1 Bender 103-1 Donelian 103-1 Godold 103-1Godbold 103-1 Bowlus 103--1 Spagnoletti 103-1 Richter 103-1 Swanson13-33 Dickson 13--33 Findlay 103-1 Baker 103-1 Yevck 103--1 FOREIGNPATENTS Great Britain.

LAURENCE V. EFNER, Primary Examiner.

1. AN ELECTROMAGNETIC PUMP SYSTEM FOR PUMPING ELECTRICALLY CONDUCTIVELIQUIDS COMPRISING: (A) FIRST AND SECOND GENERALLY CUP-SHAPED MEMBERS,(B) A RIM PORTION ON SAID FIRST CUP-SHAPED MEMBER COOPERATING WITH A RIMPORTION ON SAID SECOND CUPSHAPED MEMBER TO NEST SAID FIST MEMBER WITHINSAID SECOND MEMBER IN A SPACED APART RELATIONSHIP TO EACH OTHER, (C) APUMP REGION DEVELOPED BETWEEN SAID FIRST AND SECOND MEMBERS, (D) ATLEAST ONE INLET PORT TO SAID PUMP REGION IN SAID SECOND MEMBER, (E) ATLEAST ONE OUTLET PORT FORM SAID PUMP REGION, (F) A FIELD WOUND HELICALROTOR ROTATABLY POSITIONED WITHIN SAID FIRST CUP-SHAPED MEMBER ANDSPACED THEREFROM TO DEFINE A COOLANT FLOW PATH, (G) SUPPORT MEANS FORSAID HELICAL ROTOR INCLUDING A BEARING ARRANGEMENT REMOVED FROM SAIDFIRST CUPSHAPED MEMBER,